This invention relates to optical communication systems and more particularly to a process for making optical transceiver arrays.
Optical couplers are now used to communicate optical signals over short and long distances between, for example, two computers, two circuit boards in one computer, and even two different chips on the same circuit board.
Integrated circuit technology that enables bi-directional, high-speed optical rather than electrical interconnections has been developed. This technology allows laser emitters and detectors to be integrated onto a semiconductor substrate, making electrical connection with electronic circuitry previously built on that substrate.
Thus, optical rather than electrical communications between electronic devices is accomplished. An optical transmitter-receiver module, or optoelectronic device, typically includes both light emitting devices such as vertical cavity surface emitting lasers (VCSELs) and light detecting devices such as photodiodes. Such a module more typically may include separate chips, or the VCSELs and the photodiodes may be grown on the same substrate. See U.S. Pat. No. 5,978,401 incorporated herein by this reference.
Driver-receiver circuit modules, typically in the form of ASIC chips, include driver circuitry which receives electrical signals from an electronic device and drives the VCSELs accordingly. The ASIC chips also include receiver circuitry for receiving signals from the photodiodes and processes those electrical signals providing an appropriate output to the associated electronic device.
The combination of the VCSELs and the photodiodes and the ASIC circuitry is typically called an optical transceiver. One way to hybridize the VCSELs and the photodiodes and the ASIC receiver circuitry is by flip-chip bonding. See U.S. Pat. No. 5,858,814, incorporated herein by this reference.
These different types of photonic devices, e.g., emitters and detectors, however, have very different epitaxial layer constructions and physical dimensions, and it is not economically feasible to grow such dissimilar devices on the same substrate. Therefore, separate growth steps must be performed for each device type. This method, in turn, restricts the number of different device types integrated onto the same silicon substrate.
It is therefore an object of this invention to provide a method for making a hybrid optoelectronic device with multiple types of photonic devices, such as emitters and detectors, integrated on the same silicon substrate.
It is a further object of this invention to provide a method of making a hybrid optoelectronic device with multiple types of photonic devices interdigitated on the same silicon substrate.
This invention results from the realization that an interdigitated array of photonic devices with at least two different photonic devices of different physical and epitaxial layer construction, can be produced with good electrical and mechanical interconnections by using a multistep hybridization process including the use of sacrificial, or dummy, devices in at least a first array of photonic devices. The sacrificial devices are removed before a second array of photonic devices is hydridized with the first array.
The present invention provides a method of making a hybrid optoelectronic device. The primary steps are hybridizing a first substrate and a second substrate, the second substrate including at least one first optical device and at least one sacrificial device and introducing a first flowable hardenable material to join the first and second substrates. The first flowable hardenable material is then cured. The second substrate is then removed as is the at least one sacrificial device. The method also includes hybridizing the first substrate and a third substrate, the third substrate including at least one second optical device; introducing a second flowable hardenable material to join the first and third substrates; curing the second flowable hardenable material; and removing the third substrate.
The first substrate material may be silicon. The second and third substrate materials may be GaAs. The flowable hardenable materials may be curable epoxy resins.
The photonic devices may be emitters, transmitters and/or modulators. Modulators may be reflective, transmissive or absorptive and may modulate a received signal based on amplitude, wavelength or phase.